And diamonds aren't just here on Earth. Diamonds are made of carbon, and carbon is one of the most abundant elements in the universe. Scientists now believe that diamonds might be relatively common, especially at the cores of giant planets.

That goes for the eighth planet in our solar system, Neptune. "There's studies suggesting that Neptune has a diamond core," he says.

At least that's the theory. But the pressure at Neptune's center is enormous. Researchers weren't sure what that would do to a diamond.

"Before these experiments scientists just did not have the capabilities at hand to generate these high pressures," he says.

Livermore Lab has the world's most powerful laser, the National Ignition Facility. Smith and colleagues used its 176 beams to squeeze a tiny diamond target. The team got up to 50 million atmospheres of pressure, that's about 10 times the density of the Earth's core.

The diamond at the center of the capsule was at the density of lead before it was vaporized by the laser energy. The results, published in Nature, prove that diamond can withstand this kind of crushing. More studies are being planned to see how its behavior might change.

So what expensive thing can Smith target next? Maybe caviar?

"We could compress caviar to very high pressure," he says. "But probably the practical and planetary applications would be limited."

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Transcript

RENEE MONTAGNE, HOST:

Physicists have used the world's most powerful laser to zap diamonds. Even by the standards of advanced science, this sounded like an unusually pricey prospect. So we asked NPR's Geoff Brumfiel to find out exactly what they were doing.

BRUMFIEL: Yeah, that's what I thought too, until I met the real scientist behind this experiment.

RAYMOND SMITH: My name is Raymond Smith. I guess most people call me Ray.

BRUMFIEL: Not the world domination type. Smith is a physicist at Lawrence Livermore National Laboratory in California. When he looks at diamonds, he sees a scientific marvel.

SMITH: Well, you know, diamond has very special properties besides being expensive and used for jewelry, etcetera. It's the hardest substance known to man.

BRUMFIEL: And diamonds aren't just here on earth. Diamonds are made of carbon, and carbon is one of the most abundant elements in the universe.

SMITH: Potentially, there's a lot of diamonds elsewhere on other planets.

BRUMFIEL: Including the eighth planet in our solar system, Neptune.

SMITH: Yes, there's a study suggesting that Neptune has a diamond core.

BRUMFIEL: At least that's the theory. But the pressure at Neptune's center is enormous. Researchers weren't sure what that would do to a diamond core.

SMITH: Before these experiments, scientists just did not have the capabilities at hand to generate these high pressures.

BRUMFIEL: Livermore Lab has the world's most powerful laser. They let Smith use it to squeeze a tiny diamond target. He and his collaborators got up to 50 million atmospheres of pressure. That's about 10 times the density of Earth's core. As he reports in the journal Nature, they found that diamond can withstand these pressures. So what expensive thing can Smith target next? Champagne? Caviar?

SMITH: That would be interesting, yeah. We could compress caviar at the very high pressure, but probably the practical and planetary applications would be limited.

BRUMFIEL: Smith says boring, old iron is next. It is, after all, what's at the core of the earth. Geoff Brumfiel, NPR News. Transcript provided by NPR, Copyright NPR.